Ecokart Design Report of East Coast Racers. By Arunim aich

8/10/2019 Ecokart Design Report of East Coast Racers. By Arunim aich

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SAEGBU ECOKART DESIGN REPORTGaurav Nandakumar, Arunim Aich

Sathyabama University, ChennaiEast Coast Racers, Team N3

I.

ABSTRACT

The Objective of the SAEGBU ECOKART 2014 competition isto challenge student teams to conceive, design, fabricate andcompete with their own small go kart which works on electricity.The Objective of the Vehicle Design team is to build aprototype kart on an assumption that a manufacturing firm hasengaged them to design, fabricate and demonstrate one for

evaluation of the same as a product ready for production. Thevehicle is tested for its cost analysis, overall design presentations,

acceleration, braking, cornering capability, Battery backup andendurance.

II. INTRODUCTION

Every idea has an inception and with proper incubation it resultsin an accomplishment, our case is not going to be an exception.When we started with the project we were just a group ofpassionate students crazy about automobiles, but unaware of thecomplexities involved. Soon we realized that we belong to theonly Sathyabama Universi ty; with the amenities and foundry-

forge facilities available at our disposal, we can manufacturecustomized components for our kart.

The designing softwares which are being used are AutoCAD,Solid works and Inventor. Analysis and simulation will be done

using Autodesk Inventor and Solidworks. Our 11 member teamis all set to leave imprints on SAE-GBU ECOKART 2014. Ahigh performance, stylish kart is to be made with better handlingand maneuvering capabilities keeping in mind the costeffectiveness of our project. With this project we also aim tocreate a healthy and learning atmosphere in our campus.

Fig 1.

III. TECHNICAL SPECIFICATIONS:

A. Chassis

The frame has been designed considering the location of thespace required for different components, and compliance torules, and the space required by the driver to be comfortableenough to drive. Ample space is provided for driver cell,

providing space for battery, Circuits , ensuring drivers comfortand easy egress. The seat level has been lowered to lower the

center of gravity of the kart, leading to increased stability.Aluminium 6061 T6 is used which is appropriate for frame due toits machine ability and ease of fabrication. It is resistant toscaling and oxidation and has a lean, smooth finish. FusibleAlloy mandrel bending is used to bend the pipe without anycrimps. MIG or TIG welding is appropriate for welding.

As we had noticed that traditional go karts have very less safetyand is not at all aerodynamic so we have decided to make the kart

in such a way that it is satisfies all kind of race conditions. Hence,we chose F1 style styling of chassis. We have also considered the

utmost comfort and safety for the driver while designing the kart.The center of gravity of the driver is kept right in betweenof the wheelbase to ensure a proper balance for the kart whichdirectly enhances handling. While designing, the main objectivewas keeping the karts center of gravity as low as possible,generating maximum down force for greater traction and thatthe kart should meet or even exceed safety standards.

The roll cage was designed in SOLID WORKS and AUTOCAD.It has been analyzed in SOLID WORKS. The material gradechosen is Aluminium 6061 T6; this has yield strength of 276MPa and an ultimate tensile strength of 310 MPa which is verysuitable for the kind of forces the kart has to bear with. Loads

and constraints were applied in the chassis, keeping in mind thestatic and dynamic conditions that the kart will face during theheats, and to see how the chassis will respond to different raceconditions.


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Fig 2

During the design revisions the high stress areas wererevamped to reduce the stress concentration and improvethe overall rigidity of the chassis.

The chassis structure features Side Impact Membersaround the driver cockpit to maintain torsional rigiditywhile providing the driver with greater side impact

protection to ensure maximum safety. There is ampleroom for the driver for comfortable vehicle operation andease of egress if the driver needs to exit quickly in anemergency.

Keeping in consideration the race conditions mand the

rulebook constraints, the front and rear track width iskept 44 inches and 54 inches. A wider track width at thefront than the rear will provide more stability in turningthe kart into corners decreasing the tendency of the kart totrip over itself on corner entry and more resistance todiagonal load transfer. The wheel base is kept55 inches and we have chosen a bit longer kart because itprovides greater stability, traction and maneuvering

ability, the overall length of the kart is 76.14 inches.

The basic chassis is based on backbone Structure which

has been integrated to tubular space frame. The front

wheels will be mounted to the space frame, whereas the

rear wheel and the axis will be mounted on 4 parts of theface frame and the stem so that the stress is divided easily.

We are also providing support for the drivers head and

body is the form of head rest and back rest so that if the

kart topples theres no injury to the driver.

We have also provided place for foldable steering

attachment and adjustable steering attachment.

All over this chassis design has been tested with the help of

simulation and all the problems were corrected to give the

best possible design.

See the attached figures for the diagram of the chassis.

B. Steering

An efficient steering system is very essential for betterand smooth handling of any vehicle. We have selectedtype steering system because of its simple design,compactness and easy availability. Due to its simpledesign as compared to other types like re-circulating ball,

worm and sector etc. its mounting becomes easier andweight gets reduced because of less number of linkagesused. Understanding the importance of steep turns aroundthe corners we have tried to achieve 100% Ackermangeometry and the steering gear ratio as 12:1. Apartfrom this, detachable steering wheel hub will be used toensure quick egress in case of emergency. We have alsoapplied foldable steering for proper egress inside the kart.

The various parameters of steering system specificationsare as follows.

Caster 4Positive

Steering Ratio 12:1

King-pin inclination 2

Toe In 2.4 mm

Average Steer Angle30.55

0

Turning Radius 3.38m

Ackermann Angle36.027

0

Table 1

Steering systems are essential to provide vehicle

safety, steering quality, and steering control. The

steering column connects the steering wheel to the

steering gear. The steering wheel is connected to the

steering shaft, and this shaft extends through the


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centre of the steering column. The lower end of the

steering shaft is connected through a universal joint

or flexible coupling to the shaft from the steering

gear. The steering shaft is supported on bearings in

the steering column.

The most conventional steering arrangement is to

turn the front wheels using hand operated steering

wheel which is positioned in the front of the driver

which may contain the universal joints to allow it to

deviate somewhat in a straight line.

Steering linkages connect the steering gear to the

steering arms on the front wheels. In a parallelogram

steering linkage, a pitman arm is connected from the

steering gear to a centrelink. A pivoted idler arm

bolted to the chassis supports the other end of thecentre link. Tie rods are connected from the centre

link to the steering arms attached to the front wheels.

Pivoted ball studs are mounted in the inner ends of

the tie rods, and outer tie rod ends are threaded into

the tie rod adjusting sleeves. The outer tie rod ends

contain pivoted ball studs, and these tapered studs fit

into matching tapered openings in the outer ends of

the steering arms. The pitman arm and idler arm

position the centre link so the tie rods are parallel to

the lower control arms. The is tie rod position is very

important to maintain proper steering operation.

In here the arrangement made is according to the

Ackermann principle (kinematic steering) and the vehicle

is afront-wheel-steering4WSvehicle.

For the ecokart there is no change in the condition and the

kart wiil satisfy to Ackermann Condition.

Fig 3

In the above case :

W=king pin center to center distance

L=wheel base

R=turning radius

A2=centre of gravity from rear axle

=inner angle

=outer angle

1 Mechanism

Fig 4

2 Elaborative Calculations:


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Fig 5

TAN Angle = king pin center to center disWheelbase

Tan angle=40/55

=36.0270(ACKERMANN ANGLE)

3. Calculation of average steer angle:

R=

972=272+552*cot2

cot2

=2.869

cot =1.694

=30.550

(the average steering angle)

cot=coto+coti/2

2*1.694= coto+coticoto+coti=3.389---------------------------(icoto-coti= w/l

coto-coti =44/55

coto-coti =0.8------------------------------(ii

adding the equation (i)and (i)

coto+coti =3.389

coto-coti =0.8

2 coto =4.189

coto=2.0945

tance/2

o=25.570

puting the value of o=2

i=37.800

4. Calculation of T

sin(36.027)=y/66sin(36.027)=yy=3.528"

Note: Hence the tie rod l

5. Turning Radius

Turning radius = (track/angle))turning radius=(44/2)+(radius=130.20" (or)3.30

6. Steering Mecha

The diagram illustratescalled a lever arm stesteering system, large

.570in the equation (ii)

Fig 6

ie ROD

ength is 3.528"

alculations

2)+(wheelbase/sin(average steering

5/sin(36.0270))

m

isms

Fig 7

steering linkage that sometimes isering system. Using a lever armsteering angles at the wheels are


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possible. This steering system is used on trucks with largewheel bases and independent wheel suspension at the frontaxle. The steering box and triangle can also be placedoutside of the axles centre.

Fig 8

Some steering columns are designed so the driver can tilt

the steering wheel downward or upward to provide

increased driver comfort and facilitate entering and exiting

the drivers seat.

C. Brakes

We have selected disc type brakes for our kart because ofits simple mechanism, easy installation, better coolingefficiency, uniform pressure distribution and lighter

weight. The braking system has to provide enoughbraking force to completely lock the wheels when the

brakes are applied. We will use diagonal split brakesystem. A front/rear split system uses one mastercylinder section to pressurize the front caliper pistons andthe other section to pressurize the rear caliper pistons. Italso has an edge to other braking systems as for safety

reasons; if one circuit fails, the other circuit can stopthe vehicle. The connections are such that the left frontand the right rear brake are on one circuit and the rightfront and left rear are on the other circuit.

For selecting the master cylinder, caliper and rotor,calculation was done assuming A brake pedal over-travelswitch is planned to be installed which will kill theignition and cut the power.

D. Wheels

Wheel end is one of the main aspects to be consideredfor proper motion of the vehicle as it houses the mainmounting points of steering, suspension and brakes withthe wheel in a kart. The wheel end is made up of thefollowing parts- Rim, Hub, Disc, Milled bearing, andupright in sequence.Their compatibility with each other is a majordesign issue as these parts have been taken fromdifferent sources. Larger and broader tire is used forbetter grip and better traction.

Table 2

Brake PedalRatio

4:1

Static LoadDistribution

0.55 kg

Braking Force 6.8479 kN

Relative CentreOf Gravity

0.0166 m

AverageDeceleration

(-)2.37 ms-2

StoppingDistance

5.001 m

Brake on time 0.36 sec

Average Power 19.616 kW

Kinetic Energy 212.5 kJ

S.NO TECHNICAL DRAFTSFOR WHEEL

VALUES

1 Rim circumference 785mm

2 Rim outer diameter 125mm

3 Rim width 130mm

4 Number of lug nuts 3*4

5 Front Tire height 250mm

6 Front Tire width 132mm

7 Type of tire slick

8 Rear tire height 275mm

9 Rear tire width 175.5mm

10 Front tire pressure 0.7 1.1 bar

11 Rear tire pressure 0.75 1.2 bar


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min = 0.505 d1 = 4.2976 mm.

Roller setting angle (alpha) = 140-90/degrees. Max.

min= 120-90/T2=117.49 degrees.

Top diameter Da = D2 + 1.25 p d1 (max)= D2 + (p(1-1.6/T1)-d1

Root diameter Dr = D2 2 (ri).

Tooth width (bf1) = 0.95 b1. when p>=12.

Hence , a silent chain of above specificatifor the drive unit of the eco kart fefficiency. Calculations are done basedspecifications from the respective depamodification can be done whenever requir

Fig 9Multi-clutch is a basic mechanism where t

two different wheels in the rear axle are act

same time by a single clutch pad.The entire

shown in the fig. It consists of a clutch padwith an aluminium rod which is capable of

& fro motion, when the pad is being presse

driver.This main rod is connected to two ot

same diameter by means of a ball joint. The

these two small rods are connecting the clut

in-turn holds the pressure pads against their

flywheels.The entire assembly is similar to

so when there is linear motion in the main r

that are attached to this by means of the ball

move to pull the friction plate assembly thu

engaged by the driver i.e; the clutch disengflywheel.

When the driver releases the pressure given

rods retrace their path and move the friction

and thus the driver disengages the clutch i.e

engaged to the flywheel.The mechanism is

normalclutch that is being use in any 4-wh

1 = 138.14

&(min).

mm.

ns Is selectedr maximumon obtained

rtments. Anyd.

o clutches for

ated at the

assembly is as

hat is boltedmoving in a to

by the

er rods of

other end of

ch plates which

respective

he letter Y and

d, the two rods

joints will

s the clutch is

ges from the

on the pad the

plate assembly

; the clutch is

imilar to a

elers. But the

innovation made here is

attached to two different

avoid the variation in th

while turning at any desi

The individually attachesimultaneously using a c

these two clutches.This

turn without skidding an

variation is manipulated

is no chance for any one

other wont engage. This

together in the same mai

flywheels are attached t

equidistant from the po

This is to ensure that the

much twisting under lo

F. Electricals and Elec

1. Componants:

a) Battery

An assembly of 4 L20AHr are employedX 20 = 960W.

b) 4 Quadrant chopper

4 Quadrant Chopper Fu

a. Normal forwar

b. Regenerative b

two clutches are individually

tyres in the rear. This is made to

rotating speed of the wheels

red angle with respect to the track.

d clutches are actuatedommon clutch pad which links

nsures that the driver makes a safe

d the inner & outer wheels speed

to make them turn properly.There

clutch to get engaged and the

is because they both are connected

n rod.The clutches & the

the axle or the driven shaft

int where the sprocket is mounted.

driven shaft doesnt undergo

d.

tronic

ead Acid batteries rated at 12V,o generate a total power of 4 X 12

Fig 10

ctioning

operation

eaking


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c. Reverse operation

d. Reverse regenerative breaking

c) Controller

The controller will control the speed of the motor. The

gradual increase and decrease in the speed of the motor is

done by the controller. This is done by fast ON OFF

switching action. This switching action is done by the

switching MOSFETS. The technique used to control the

speed in the controller is PWM (Pulse width modulation)

technique. The rapid switching action of the MOSFETS

causes the heating up of the controller. This heat can be

dissipated by using a mechanical heat sink.

d). BLDC motor

The power rating of the motor is 800W.

2 Specifications

Table 4

3. Performance

The input electrical power is supplied by the battery bank

of 4 batteries, rated at 4*12V, 20Ah.

The mechanical power out is fed to the drive train to

produce translational motion.

Total electrical Power generated = 4*12V*20Ah = 960Wh

Total power of the motor = 800W. [Permissible max power

output]

a). Discharging time

Electric power output of the battery=48*20=960Wh

Power consumed = 800W (by 800W motor)

Total time taken by the motor to get discharged = 960/800

= 1.2hrs(at optimum usage)

b) Charging time

Points of consideration

1.

Cells can easily tolerate a sustained chargingcurrent of 1/10 of the cell's A-hr rating with nodamage to the cell.

2. We can consider of the cells A-hr rating but it

may reduce the life of the battery.

According to the points of consideration

Charger capacity : 48V,3.3Ah

Power output by the charger = 48*3.3 = 158.4Wh

Total power output of the battery = 960W

Time taken to charge the battery = 960/158.4 = 6.060 hrs

Therefore, Total Charging time will be 6hrs approximately.

c. . Kill Switch

It is used to disconnect all the circuits and the motor from

the battery supply in case of an emergency. Kill switch

will be connected after the battery then to the other

circuits.

3 kill switches are used and these are placed at 3 places as

explained below:

Near the steering

Rear part of the seat

On the left side of the vehicle

4. Sensors

a) Hygrometer

A hygrometer is an instrument used to measure the specific

gravity (or relative density) of liquids; that is, the ratio of

the density of the liquid to the density of water. This will

indicate the percentage level of charge of the battery.

MOTOR BLDC MOTOR , 800W

BATTERY LEAD ACID BATTERIES,12V*4 = 48V,20Ah

CHARGING TIME 6-8 hrs

CHARGER CAPACITY 48V,3.3Ah

DISCHARGING TIME Optimum discharge time

=1.2hrs

REAR LIGHTS LED STRIP AA Batteriesused

SPECIFIC GRAVITY PERCENTAGE OF CHARGE

1.265 100%

1.225 75%

1.155 25%


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b) Motor Temperature

We use a reference voltage(vref) and a thermistor to detect

the heat. Then compare the v(ref) with the thermistor temp.

the obtained data is compared with the pre-set level to

switch on the fan to cool the motor avoiding excess heating

of motor and ensure less losses and better

efficiency.Thermistor working temp-90-130*cDepending

upon the motor temperature and the voltage it will rise or

fall.The pre-set resistor can be turned up or down to

increase or decrease resistance, in this way it can make the

circuit more or less sensitive.

c). Distance Indicator

It is used in a special way to indicate the distance left toreach a particular destination.

d) Speedometer

It will be used to inform the driver the speed of the kart atdifferent time intervals.

G. Bodyworks

The Body of the kart has been designed fromaerodynamic point of view and style matters to us.Curves will be such that it would lessen the vortices

generated, it will be good looking and eye catchy. Frontwings will be installed as per aerodynamic point.Among choices like FRP or Sheet metal, FRP ischosen as the body material due to its aesthetic nature,lighter weight and ease of fabrication. It is alsodifficult to get good body curves with sheet metal.Sheet metal has however been chosen to cover thebase and as firewall since they are well protected andneed no curves and were to be covered properly. Thedrivers seat is designed keeping in mind thebetter seating posture as well as to lower the COG.Also the design of the kart ensures maximum visibilityduring driving, two rear view mirror installed in the

nose maximizes the view to 210. 300mm lengthImpact attenuator will be installed on the frontbulkhead will be made from aluminum honeycombwhich will absorb the impact energy during the time ofcrash. Instrument panel will comprise of heat/oilindicator, tachometer and speedometer, it will drive itsreadings from ECU.

III. SAFETY

Collision Measures:

Front Bumpers and Honey combstructured Impact Attenuator

Rear Bumbers, Rear anticollisiondesign and Rear Wheel

Side Side Impact Frame Member(Roll over Member), impactattenuators on both sides as20kgs batteries.

Driver Safety Seat Belts; Helmet; DriverSuits, ErgonomicallyDesigned Chassis; Guards;Fully Guarded Chains

Bystanders

andPedestriansSafety

Powerful Disc Brakes; Kill

Switch

Kill Switch 3 switches reachable to boththe drivers as bilateral seating

ElectricalSafety

All wiring insulated; Motorcan be used for emergencybraking

TABLE 6V. ERGONOMIC FEATURES

1. Quick Release of Steering which helps the driver to get

our of the kart quick.

2. We are not using the traditional design of a kart, ratherwe have used a design which is improves bothaerodynamics as well as safety.

3. We have Introduced foldable steering techniqueswhich improves the egress of the vehicle.

4. Adjustable steering to the drivers comfort.

5. For better ventilation of the driver we have addedstainless steel mesh at front.

6. Seat has been reclined to an angle of 30 degrees whichis best suitable for racing vehicles.

7. Special care has been taken for avoiding commoninjuries while driving of the kart, for exampleintroduction of lumber support for leg stiffness.

8. Ample leg room has been provided for comfortmovement of the driver.

adverse conditions and most importantly, we believe inourselves that we can make anything possible with our


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intellect, intuition and incisiveness. We are all set tomeet the challenges ahead with an affirmation tosteer through.

VI. ACKNOWLEDGEMENT

EAST COAST RACERS, TEAM N3 is thankful toDr. S. Prakash, HOD, Mechanical and ProductionDepartment for his constant support, guidance and

motivation which keep our spirits high and fortechnical guidance and expertise which always keeps usgoing.

VII. REFERENCES

We have referred to various websites, e-books, design

reports, papers and online tutorials to make our report.

They were really helpful and guided us in the

completion of this report.

Some of them are:

1.

Automobile Mechanical and Electrical Systems - T.Denton (B-H, 2011) BBS

2.

Automotive Engineering Powertrain, Chassis Systemand Vehicle Body-David E Corolla

3.

Fundamentals of Vehicle Dynamics-Thomas D. Gillespie

4. Automotive Engineering Lightweight, Functional andNovel materials-Brian Cantor.

VIII. CONCLUSION

This being our first SAE-GBU ECOKART projectmeans a lot to us. This also matters significantlybecause it would lay a foundation stone in our collegewhich would always actuate the coming batches tokartry on the legacy. During these days of preparationfor the ECOKART project, we went through aprocess of quality learning which are helping usspearheading. We are full of enthusiasm andconfidence that we are going to experience a wholenew adventure which would let us broaden ourvision and thoughts. Each and every team member is

dedicated and willing to give their best to with

IX. CONTACT

Arunim Aich B.E. V I (MPE),

Sathyabama Univeristy,[email protected]

Gaurav Nandakumar, B.E VI (MPE),Sathyabama University, Chennai

[email protected]


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X. VIEWS


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Fig 11. Top View

(AUTOCAD 2013 Students Edition)


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Fig 12 Front View(AUTOCAD 2013 Students Edition)

Fig 13 Right Side View(AUTOCAD 2013 Students Edition)


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Fig 14. SE Isometric View(AUTOCAD 2013 Students Edition)

Fig 15. NE Isometric View(AUTOCAD 2013 Students Edition)


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Fig 16. NE isometric Rendered Image (AUTOCAD 2013 Students Edition)

Fig 17. Front View Rendered Image (AUTOCAD 2013 Students Edition)

XISTRESS ANALYSIS (PRE CORRECTION IMAGES)


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FIG 20

FIG 21

Ecokart Design Report of East Coast Racers. By Arunim aich

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